The present invention relates generally to the making of electrical signal connections between circuit boards and, more particularly, to a technique for electrically interconnecting signals between circuit boards.
In many computer systems, electronic components are typically mounted on a plurality of circuit boards. These circuit boards, often referred to as daughterboards, are typically mounted on a motherboard so as to allow electrical connections to be made between the electronic components mounted on the daughterboards. The mounting of the daughterboards on the motherboard is typically accomplished through conventional pin-and-box connectors. However, there are intrinsic and mechanically related parasitics associated with these conventional pin-and-box board-to-board connectors. This type of connector, due to mechanical design constraints, is inherently bandwidth limited by parasitic elements of excess capacitance and inductance. These parasitics put limits on maximum signal transmission bandwidth across the mother and daughter boards. In fact, the best connector that is presently known in the industry claims to be able to handle 5 Gb/s, which cannot meet the bandwidth demands associated with new telecommunication systems, which are on the order of 10 Gb/s.
There are also space concerns associated with the use of conventional pin-and-box board-to-board connectors. That is, conventional pin-and-box board-to-board connectors typically have bulky mechanical shrouds which take up valuable board and shelf space.
An additional problem that occurs during transmission of signals with high frequencies is cross-talk between adjacent signal conductors as further explained in U.S. patent application Ser. No. 09/443,128. This problem is particularly troublesome at high data rates such as 10 Gb/s.
In view of the foregoing, it would be desirable to provide a technique for making electrical signal connections between circuit boards which overcomes the above-described inadequacies and shortcomings. More particularly, it would be desirable to provide a technique for electrically interconnecting signals between circuit boards while eliminating problems associated with mechanical electrical connectors.
According to the present invention, a technique for electrically interconnecting a signal between a first circuit board and a second circuit board is provided. In one embodiment, the first circuit board has a first signal conductor or set of signal conductors formed therein, and the second circuit board has a second signal conductor or set of signal conductors formed therein. Also, the first signal conductor is shielded by a first electrically conductive shield, and the second signal conductor is shielded by a second electrically conductive shield. In this embodiment, the technique is realized by forming a first opening in the first electrically conductive shield so as to expose the first signal conductor in the first circuit board, and forming a second opening in the second electrically conductive shield so as to expose the second signal conductor in the second circuit board. An electrically conductive adhesive, solder paste, or interposer/elastomer device is then applied around at least one of the first and second openings and within at least one of the first and second openings. The first circuit board and the second circuit board are then positioned such that the first opening and the second opening are aligned and a signal propagating along the first signal conductor is electrically interconnected to the second signal conductor.
In accordance with still further aspects of the present invention, wherein the signal is a first signal, the first circuit board may have a third signal conductor formed therein, and the second circuit board may have a fourth signal conductor formed therein. The third signal conductor may be shielded by a third electrically conductive shield, and the second signal conductor may be shielded by a fourth electrically conductive shield. Then, a third opening may beneficially be formed in the third electrically conductive shield so as to expose the third signal conductor in the first circuit board. Also, a fourth opening may beneficially be formed in the fourth electrically conductive shield so as to expose the fourth signal conductor in the second circuit board. Further, the first circuit board and the second circuit board may beneficially be positioned such that the third opening and the fourth opening are aligned and a second signal propagating along the third signal conductor is electrically interconnected to the fourth signal conductor. Typically, the third electrically conductive shield is electrically connected to the first electrically conductive shield, and the fourth electrically conductive shield is electrically connected to the second electrically conductive shield.
In accordance with still further aspects of the present invention, the first circuit board may be a motherboard, and the second circuit board may be a daughterboard. The daughterboard is beneficially formed at least partially of flexible material so as to hollow angular mating with the motherboard.
In an alternate embodiment, the first circuit board has a first signal conductor formed therein, and the second circuit board has a second signal conductor formed therein, but only the first signal conductor is shielded by an electrically conductive shield. In this embodiment, the technique is realized by forming an opening in the electrically conductive shield so as to expose the first signal conductor in the first circuit board. The method is further realized by applying an electrically conductive adhesive, solder paste, or interposer/elastomer device surrounding the first opening and within the first opening. The first circuit board and the second circuit board are then positioned such that the first signal conductor and the second signal conductor are aligned through the opening and a signal propagating along the first signal conductor is electrically interconnected to the second signal conductor.
The present invention will now be described in more detail with reference to exemplary embodiments thereof as shown in the appended drawings. While the present invention is described below with reference to preferred embodiments, it should be understood that the present invention is not limited thereto. Those of ordinary skill in the art having access to the teachings herein will recognize additional implementations, modifications, and embodiments, as well as other fields of use, which are within the scope of the present invention as disclosed and claimed herein, and with respect to which the present invention could be of significant utility.